Before playing an instrument or singing, the player, singer, etc. adjusts the pitch for playing or singing musical notes correctly based on a reference tone using a tuning fork or a tuner.
Besides, when playing an instrument, the player or the like has to tune the instrument in advance so that it plays at the correct pitch. In this case, the player tunes the instrument while checking the pitch of each note with a tuning meter. Consequently, the player is required to carry the tuning meter into a venue for a concert each time he/she gives a performance as well as to take care of it.
If a cellular phone, which has been in widespread use, has a tuning function as for example described in Japanese Patent Application laid open No. 2002-49368, the player need not carry around the tuning meter.